This invention relates generally to electrically driven fluid pumps, and more particularly to electrically driven centrifugal pumps which require no shaft seals.
Centrifugal fluid pumps are well known in the hydraulic and pneumatic fields. They commonly consist of a motor to drive a shaft on which a fluid impeller is mounted. Generally, the fluid inlet port, or suction port, feeds fluid to the center, or hub, of the impeller. A number of impeller vanes generally project outward from the hub in spiral paths and are supported between shrouds which, together with the vanes, define pumping channels. The rotor is encased in a housing which channels the working fluid from the inlet port to the hub, or inducer, where it is inducted into the pumping channels between the vanes and shrouds. The centrifugal action of the impeller drives the working fluid outward to a diffuser at the periphery of the impeller disk where it enters a scroll shaped volute and, from there, is channelled to the discharge port of the pump.
The motor shaft, which supports the impeller, requires bearings which are sometimes lubricated by the working fluid, but, in many cases, they require separate lubrication due to incompatibility of the working fluid. In all cases, seals are required to prevent leakage of the working fluid around the impeller shaft where it enters the pump housing. After some time in service, the bearings may deteriorate to the point where they permit some radial displacement of the rotating shaft. This causes accelerated wear and deterioration of the shaft seal and results in leakage of the working fluid from the pump housing.
The foregoing illustrates limitations known to exist in present centrifugal pumps. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.